n = 0
for i in range(2, 100, 2):
    n += i
print(n)
---------------------------
for i in range(100, 20, -3):
    if i % 2 != 0:
        print(i)
-------------
frase = input()
flag = True
for i in frase:
    if flag == True:
        print(i, end="")
    flag = not flag

print()
for i in range(len(frase)):
    if i % 2 == 0:
        print(frase[i], end="")
print()
for i in range(0, len(frase), 2):
    print(frase[i], end="")
print()
print(frase[::2])